The difference is 1,020lbs.
Maybe it's an on board astronomical observatory.
The radio equipments is listed as:
C-1 Radio SCR-274N @ 82lbs
C-2 Radio SCR-522 @ 96lbs
C3 Radio SCR-695 @ 38lbs
C-4 Radio SCR-535 @ 32lbs
Radio Instruction Book @ 1lb
Total weight - 249lbs
These components and their weight are already figured in the "Combat Condition" check list.